Motor drive for sewing machines

ABSTRACT

There is disclosed a sewing machine adapted to be driven by an electric motor supported from the sewing machine bed on cantilever brackets which extend beneath the machine supporting work tables rearwardly of the hinges by which the machine is pivotally mounted on the work table. In combination with the length and small diameter of this motor, this physical arrangement of the motor provides advantageous leg room for a machine operator, and permits pivoting the machine back for inspection and the like without disturbing the driving relationship of the motor to the sewing machine.

United States Patent [191 Wendel 1 MOTOR DRIVE FOR SEWING MACHINES [75]Inventor: Lorenz A. Wendel, Somerville, NJ.

[73] Assignee: The Singer Company, New York,

[22] Filed: Feb. 24, 1975 [21] Appl. No.: 552,466

[52] US. Cl. 112/217.1 [51] Int. Cl. D05B 75/00 [58] Field of Search112/217.l, 258, 260

[56] References Cited UNITED STATES PATENTS 1,783,836 12/1930 Finlayson112/217.1 X 1,792,361 2/1931 Christensen 112/217.1

2,477,433 7/1949 Webb 112/258 2,899,249 8/1959 Kishibay 112/217.1

FOREIGN PATENTS OR APPLICATIONS 957,419 8/1949 France 112/260 Dec.9,1975 355,342 8/1961 Switzerland 112/260 Primary Examiner-George H.Krizmanich Attorney, Agent, or Firm-Edward L. Bell; Robert E. Smith;Marshall .I. Breen [57] ABSTRACT There is disclosed a sewing machineadapted to be driven by an electric motor supported from the sewingmachine bed on cantilever brackets which extend beneath the machinesupporting work tables rearwardly of the hinges by which the machine ispivotally mounted on the work table. In combination with the length andsmall diameter of this motor, this physical arrangement of the motorprovides advantageous leg room for a machine operator, and permitspivoting the machine back for inspection and the like without disturbingthe driving relationship of the motor to the sewing machine.

5 Claims, 2 Drawing Figures U.S. Patent Dec. 9 1975 Sheet 1 of23,924,552

US. Patent Dec. 9 1975 Sheet 2 of2 MOTOR DRIVE FOR SEWING MACHINESBACKGROUND OF THE INVENTION This invention relates to sewing machines,particularly of the industrial type, and to the electric motor drivemeans therefor. In sewing machines for household use the speed ofoperation of the sewing machine does not play an important role.However, in the use of industrial type sewing machines it is necessaryto run the machine at a high speed and this high speed must be obtainedinstantaneously with the start of the machine. Traditionally, in suchsewing machines an electric motor driven power transmitter is used todrive the sewing machine. Such a power transmitter forms the subjectmatter of the US. Pat. No. 3,738,462 issued June 12, 1973. In use therotor shaft of the power transmitter runs continuously and a clutchmechanism is used for coupling the sewing machine to the continuouslyrotating rotor shaft. Thus, the sewing maching will run at full speedalmost immediately after shifting of the clutch to the driving position.In order to stop the sewing machine as instantaneously as it is started,the clutch is arranged to be shifted to engage a brake member. Themachine will therefore also stop substantially instantaneously.

As is customary the sewing maching is supported in a cut-out provided inthe table top of a power table assembly, and the power transmitter issupported beneath the table top close to the rear edge thereof. Thepower transmitter is connected by an endless belt to the main shaft ofthe sewing machine. One of the disadvantages of this type of drive isthat each time the sewing maching is tilted back on its hinges it isnecessary to remove the endless belt from the pulley on the sewingmaching main shaft. Several other disadvantages that exist arenonuniform torque output resulting from imput mechanical shock caused byclutch, brake and belt action. Also the operating performance of thesewing machine varies as a function of clutch, brake, belt and pulleywear. Further, the motor continually consumes energy during periods whenthe sewing machine is idle.-

With the introduction of low-inertia, moving-coil and surface-woundannature DC. motors during the past few years, it is possible toovercome all the deficiencies of the present clutch-brake powertransmitter drives. These DC. motors are equipped with rotary arrnaturesconsisting of a very low-inertia copper coil or surfacewound rotorcontaining no iron and immersed in a constant flux field preferablysupplied by permanent magnets. In actual use it is the practice toconnect a DC. motor of the above type directly to the main shaft of asewing machine and by providing controlled rectifier circuitry forsupplying a controlled direct current to the motor for deriving adriving torque, or selectively, by supplying an electrical load to thearmature for deriving a dynamic braking torque from the motor, all thefunctions presently performed by flywheel induction motors with clutchand brake can be performed in equal or better manner and without thedisadvantages inherent in the above described power transmitters. A DC.motor used on a sewing machine as above described forms the subjectmatter of the US. Pat. No. 3,597,672 issued Aug. 3, 1971 and US. Pat.No. 3,667,413 issued June 6, 1972.

With respect to the use of direct drive D.C. lowinertia motors, it hasbeen discovered that the armatures of these motors, having a very thindisc-like construction and having just a minimum of copper, are veryfragile and are prone to self-destruction. The high pulse currentrequired in starting and stopping the sewing machine develops in thearmature considerable heat which must be dissipated as quickly aspossible. It has been determined that without air cooling the maximumnumber of sewing machine starts and stops is approximately 16 perminute, and if cooling is provided a maximum number of 40 starts andstops is the limit.

SUMMARY OF THE INVENTION It is the primary object of the presentinvention to provide a sewing apparatus including a power table having atable top provided with a sewing machine receiving cut-out, a sewingmachine mounted in said cutout and having a rotary main shaft, hingemeans supporting said machine on said table top providing for tiltingsaid sewing machine backwardly to expose mechanism within the bed of thesewing machine, at least one motor supporting bracket secured to saidsewing machine beneath the table top and disposed to extend downwardlyand rearwardly of the cut-out, a motor secured to said bracket, and beltmeans connecting said motor to said sewing machine main shaft, saidmotor dimensioned and connected to said bracket so that the sewingmachine may be tilted back on its hinges without removing the belt meansfrom the sewing machine and the motor and without having interferencebetween the motor and the table top in the movement of the machine fromits operative position to its tilted back inoperative position.

This object is attained by the inclusion of an electric motor in whichthe diameter of the motor armature is considerably smaller than thelength of the armature. The result of this motor configuration is a lowinertia motor having a small vertical height, permitting the motor to besupported directly by the bed of the sewing machine without encroachingon the space occupied by the legs of the sewing machine operator.

BRIEF DESCRIPTION OF THE DRAWINGS The above object and advantages of theinvention will become apparent from the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a front elevational view, partly in section, showing a portionof the power table with the sewing machine resting in the cut-out in thetable top, the motor fastened on the machine bed, and the belt drivefrom the motor to the main shaft of the sewing machine; and

FIG. 2 is a left end elevational view, partly broken away, showing infull lines the sewing machine and its driving motor disposed in thenormal operative position, and in dotted lines the sewing machine andits driving motor in the hinged back position of the sewing machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to theaccompanying drawings wherein like reference numberals denote similarparts, there is disclosed a conventional power table, indicated as 10,having a table top 11 provided with the usual machine cut-out l2.Disposed within the cut-out 12 is the bed portion 13 of a sewingmachine, preferably of the industrial type. The bed portion 13 is formedwith a depending rear wall 13' which extends substantially the 3 fulllength of the bed 13. The sewing machine. as is usual, has an upstandingstandard 14 that merges into an overhanging bracket arm 15 terminatingin a head 16in which is journaled for endwise reciprocation: a needlebar 17 carrying a needle 18. Journaled in the bed 13 is a rotary mainshaft 19 connected by a belt 20 tlo5 a rotary arm shaft 21 journaled inthe bracket arm Secured to the rear wall 13' of the bed 13 of the sewingmachine, by means of cantilever brackets 2222, is an electric drivingmotor 23 having mounted on its rotor shaft 24 a toothed belt pulley 25.Through the use of the brackets the motor is fixed in unitaryrelationship with the sewing machine, the brackets being formed so thatthe motor 23 is located behind the rear wall 13'of the bed and alsobehind the pivotal axis of the hinge means 28. The belt pulley 25 isconnected by a belt 26 to a toothed pulley 27 faston the bed shaft 19.In its preferred form the electric motor 23 is a permanent magnet D.C.low inertia motor having an armature of small diameter and appreciablelength. This ratio of armature length to armature diameter issubstantially 3 to l or greater and this contributes materially to theadvantages gained from the present invention. Firstly, the smalldiameter results in a low inertia drive, whereby extremely fast startsand stops can be obtained and the clutch-brakearrangement of theconventional electric transmitter can be eliminated. Further, thevertical compactness of the motor allows it to be supported in dependingfashion on the bed of the sewing machine as clearly shown in FIG. 2. Itwill be noted that when the sewing machine is in its normal operativeposition, shown in full lines in FIG. 2, the motor is located behind thesewing machine and relatively close to the underside of the table top11. This desirable location of the motor provides considerable leg-roomfor the operator, and any heat that may be generated in the motor isdissipated without discomfort to the operator.

Another advantage flowing from the present invention is that the sewingmachine can be tipped back about hinges 28 (see FIG. 2) from its normaloperative position to an inoperative position, whereby the mechanism inthe sewing machine bed can be inspected or lubricated, without requiringthat the belt 26 be removed from the sewing machine or the motor.Moreover, the dimensions of the motor are such that the cutout 12 in thetable top 11 is minimum and only sized to fit the sewing machine bed 13.

Numerous alterations of the structure herein disclosed will suggestthemselves for those skilled in the art. However, it is to be understoodthat the present disclosure relates to a preferred embodiment of theinvention which is for the purpose of illustration only and not to beconstrued as a limitation of the invention. All such modifications whichdo not depart from the spirit of the invention are intended to beincluded within the scope of the appended claims.

Having thus set forth the nature of the invention what is claimed hereinis: p

1. A sewing apparatus including a power table having a table topprovided with a sewing machine receiving cut-out, a sewing machinemounted in said cut-out and having a bed and a rotary main shaft, hingemeans supporting said machine on said table top providing for tiltingsaid sewing machine backwardly to expose mechanism within the bed of thesewing machine, at least one motor supporting bracket secured to saidsewing machine beneath the table top and disposed to extend downwardlyand rearwardly of the cutout, a motor fixed downwardly of the cut-out, amotor fixed in unitary relation relatively to said sewing machine bysaid bracket, and belt means connecting said motor to said sewingmachine main shaft, the dimensions and unitary relation of said motor tosaid sewing machine being such that the sewing machine may be tiltedback on said hinges without removing the belt means from the sewingmachine or the motor and without causing interference between the motorand the table top in the movement of the machine from its operativeposition to its tilted back inoperative position.

2. A sewing apparatus as called for in claim 1 wherein the sewingmachine bed has a depending rear wall and said at least one hinge meansis connected to said rear wall.

3. A sewing apparatus as called for in claim 2 wherein said at least onehinge means is connected to and located behind said rear wall and saidat least one motor supporting bracket is secured to said rear wall andis so formed as to support the motor beneath and rearwardly of thecut-out in said table top.

4. A sewing apparatus as called for in claim 3 wherein the motor isconstructed so that the ratio of motor length to motor diameter issubstantially 3 to l or larger.

5. A sewing apparatus as called for in claim 1 wherein the rotary mainshaft is journaled in the bed of the sewing machine and the motor isbelt-connected to said rotary main shaft.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 23,924,552

DATED December 9, 1975 INVENTOR(S) Lorenz A. Wendel It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Claim 1, lines 19 and 20 Cancel "a motor fixed downwardly of thecut-out,"

Signed and Sealed this thirteenth Day of April1976 [SEAL] AIIeSI.

RUTH C. MASON C. MARSHALL DANN Atftstl'ng Offiter ('mnmissr'mzvruflarer'rts and Trademarks

1. A sewing apparatus including a power table having a table topprovided with a sewing machine receiving cut-out, a sewing machinemounted in said cut-out and having a bed and a rotary main shaft, hingemeans supporting said machine on said table top providing for tiltingsaid sewing machine backwardly to expose mechanism within the bed of thesewing machine, at least one motor supporting bracket secured to saidsewing machine beneath the table top and disposed to extend downwardlyand rearwardly of the cut-out, a motor fixed downwardly of the cut-out,a motor fixed in unitary relation relatively to said sewing machine bysaid bracket, and belt means connecting said motor to said sewingmachine main shaft, the dimensions and unitary relation of said motor tosaid sewing machine being such that the sewing machine may be tiltedback on said hinges without removing the belt means from the sewingmachine or the motor and without causing interference between the motorand the table top in the movement of the machine from its operativeposition to its tiLted back inoperative position.
 2. A sewing apparatusas called for in claim 1 wherein the sewing machine bed has a dependingrear wall and said at least one hinge means is connected to said rearwall.
 3. A sewing apparatus as called for in claim 2 wherein said atleast one hinge means is connected to and located behind said rear walland said at least one motor supporting bracket is secured to said rearwall and is so formed as to support the motor beneath and rearwardly ofthe cut-out in said table top.
 4. A sewing apparatus as called for inclaim 3 wherein the motor is constructed so that the ratio of motorlength to motor diameter is substantially 3 to 1 or larger.
 5. A sewingapparatus as called for in claim 1 wherein the rotary main shaft isjournaled in the bed of the sewing machine and the motor isbelt-connected to said rotary main shaft.